1. Field of the Invention
The present invention relates to a lamp driving circuit, an inverter board and a display apparatus having the inverter board. More particularly, the present invention relates to a lamp driving circuit, an inverter board and a display apparatus having the inverter board, capable of preventing a flickering phenomenon of a light from a lamp.
2. Description of the Related Art
In general, a liquid crystal display (LCD) includes a liquid crystal display panel displaying images and a backlight providing the liquid crystal display panel with light. Some backlights employ a cold cathode fluorescent lamp (CCFL) as a light source.
Recently, LCDs have utilized a dimming method to control brightness of the backlight thereof in order to increase a contrast ratio of the images displayed thereon or to decrease electric power consumption of the backlight. Dimming methods for the backlight include (i) a pulse width modulation (PWM) control method and (ii) tube current control.
In the PWM control method, the CCFL is repeatedly turned on and turned off in accordance with a duty ratio of the PWM signal. That is, the PWM control method controls turn-on and turn-off periods of the CCFL to adjust the brightness of the backlight. The tube current control method controls a voltage level applied to the CCFL to vary the tube current of the CCFL, thereby adjusting the brightness of the backlight. However, since the tube current control does not work when the tube current is low, the PWM control method has been mainly used for the LCD instead of the tube current control method.
In order to employ the PWM control method, a lamp driving circuit for a backlight receives a direct current voltage or a square wave voltage from an external device. In case of receiving the direct current voltage, the lamp driving circuit compares the direct current voltage with a triangle wave voltage that is self-generated in order to generate the square wave voltage. However, noise occurs between the triangle wave voltage and the direct current voltage, so that the square wave voltage is distorted. When the turn-on and turn-off of the lamp is controlled based on the distorted square wave voltage, the flickering phenomenon occurs on a screen of the display device that employs the lamp driving circuit.